a person of incredibly low self esteem and absolutely no morals who will allow sexual intercourse to be performed upon them for chump change, usually in the washroom at a public park or perhaps in a bar
"melissa is such a fuckbuck, she took it in every orifice at least ten times last night for two dollar fity fi and some chewing gum"
A male or female who has had so much anal sex in their lifetime that their asshole gapes open much larger than the average anus. You can detect a fuckbucket in many ways. For example, if a person farts and it sounds like someone blew through a glass bottle, that person is more than likely a fuckbucket.
Dude, did you hear that girl fart? It sounded like someone blew air through a beer bottle! Five bucks says she's a fuckbucket!